Java通过 Socket 实现 TCP服务端(一个实例)

• Java Socket简介
  
• TCPServer代码实例

1 Java Socket简介

　　所谓socket 通常也称作”套接字“，用于描述IP地址和端口，是一个通信链的句柄。应用程序通常通过”套接字”向网络发出请求或者应答网络请求。Socket和ServerSocket类库位于Java.NET包中。ServerSocket用于服务器端，Socket是建立网络连接时使用的。在连接成功时，应用程序两端都会产生一个Socket实例，操作这个实例，完成所需的会话。对于一个网络连接来说，套接字是平等的，并没有差别，不因为在服务器端或在客户端而产生不同级别。

2 TCPServer代码实例

import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.ServerSocket;import java.net.Socket;import java.util.Date;import java.util.HashMap;import java.util.Map;import org.slf4j.Logger;import org.slf4j.LoggerFactory;/** * TCP服务器端,单例模式 * @author xiang * */public class TCPServer implements Runnable {    private static final Logger logger = LoggerFactory.getLogger(TCPServer.class);    //成员变量/    private static TCPServer serverInstance;                private static Map<String, SocketThread> socketMaps = new HashMap<String,SocketThread>();　　　　　　　　//每个客户端连接时都会新建一个SocketThread与之对应   private static ServerSocket serverSocket;                    //服务器套接字    private static int serPort = 9999;                            //服务器端口号    private static boolean flag;                                //服务器状态标志    private static final int BUFFER_SIZE = 512;                    //数据接收字符数组大小        //构造函数/    private TCPServer() {            }        /**     * 获取实例     * @return TCPServer实例serverInstance     */    public static TCPServer getServerInstance(){        if(serverInstance==null)            serverInstance = new TCPServer();        return serverInstance;    }        /**     * 开启服务器     * @throws IOException     */    public void openTCPServer() throws IOException{       if(serverSocket==null || serverSocket.isClosed()){            serverSocket = new ServerSocket(serPort);            flag = true;        }    }        /**     * 关闭服务器     * @throws IOException      */    public void closeTCPServer() throws IOException{        flag = false;      if(serverSocket!=null)            serverSocket.close();        /*for (Map.Entry<String, SocketThread> entry : socketMaps.entrySet()) {               System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());                  } */         for (SocketThread value : socketMaps.values())              value.closeConnect();        socketMaps.clear();           }        /**     * 服务器向客户端发送数据     * @param bytes[]:待发送的字符数组     * @param key 客户端的key,为空或""时表示数据群发     * @throws IOException      */    public void sendMessage(String key,byte[] msgBytes){        if(key==null||key.equals("")){            for (SocketThread value : socketMaps.values())                  value.sendMassage(msgBytes);        }else{            SocketThread thread = socketMaps.get(key);            if(thread!=null)                thread.sendMassage(msgBytes);        }    }        /**     * 服务器向客户端发送数据     * @param key 客户端的key,为空或""时表示数据群发     * @param msgStr:待发送的字符串     * @throws IOException      */    public void sendMessage(String key,String msgStr){      byte[] sendByte = msgStr.getBytes();        if(key==null||key.equals("")){            for (SocketThread value : socketMaps.values())                  value.sendMassage(sendByte);        }else{            SocketThread thread = socketMaps.get(key);            if(thread!=null)                thread.sendMassage(sendByte);        }    }        @Override    public void run() {        logger.info("服务器线程已经启动");      while(true){            try {                while(flag){                    logger.info("服务器线程在监听状态中");                    Socket socket = serverSocket.accept();                    String key = socket.getRemoteSocketAddress().toString();                    SocketThread thread = new SocketThread(socket,key);                    thread.start();                    socketMaps.put(key, thread);                                       logger.info("有客户端连接："+key);                }                           } catch (Exception e) {                e.printStackTrace();                           }         }    }                 /**     * 处理连接后的数据接收请求内部类     * @author xiang     *     */    private class SocketThread extends Thread{        private Socket socket;        private String key;        private OutputStream out;        private InputStream in;                //构造函数        public SocketThread(Socket socket,String key) {            this.socket = socket;            this.key = key;        }                /**         * 发送数据         * @param bytes         * @throws IOException          */        public void sendMassage(byte[] bytes){            try {                if(out==null)                    out = socket.getOutputStream();                out.write(bytes);            } catch (Exception e) {                e.printStackTrace();                try {                    closeConnect();                } catch (IOException e1) {                    e1.printStackTrace();                }                socketMaps.remove(key);                            }         }        /**         * 关闭连接，释放资源         * @throws IOException          */        public void closeConnect() throws IOException{            if(out!=null)    out.close();            if(in!=null)    in.close();            if(socket!=null && socket.isConnected())    socket.close();        }                @Override        public void run() {            byte[] receivBuf = new byte[BUFFER_SIZE];            int recvMsgSize;            try {                in = socket.getInputStream();                out = socket.getOutputStream();                while ((recvMsgSize = in.read(receivBuf)) != -1) {                    String receivedData = new String(receivBuf, 0, recvMsgSize);                    System.out.println("Reverve form[port" + socket.getPort() + "]:" + receivedData);                    System.out.println("Now the size of socketMaps is" + socketMaps.size());                    /**************************************************************                     *                      * 接收数据后的处理过程                     *                      **************************************************************/                }                // response to client                byte[] sendByte = "The Server has received".getBytes();                // out.write(sendByte, 0, sendByte.length);                out.write(sendByte);                System.out.println("To Cliect[port:" + socket.getPort() + "] 回复客户端的消息发送成功");                closeConnect();                socketMaps.remove(key);                           } catch (Exception e) {                e.printStackTrace();                try {                    closeConnect();                } catch (IOException e1) {                    e1.printStackTrace();                }            }        }                //////////////        public int getport(){            return socket.getPort();        }    }    //. end SocketThread    }